Evaluation of numerical wave model for typhoon wave simulation in South China Sea

The simulating waves nearshore (SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea (SCS) was evaluated. A blended wind field, consisting of an interior domain based on Fujita's model and an exterior domain based on Takahashi's model, was used as the driving wind field. The waves driven by Typhoon Kai-tak over the SCS that occurred in 2012 were selected for the numerical simulation research. Sensitivity analyses of time step, grid resolution, and angle resolution were performed in order to obtain optimal model settings. Through sensitivity analyses, it can be found that the time step has a large influence on the results, while grid resolution and angle resolution have a little effect on the results.     

南海北部海域海底沙波演化特征

在对沙波的成因、形态以及运移机制充分探讨的基础上,给出了预测计算海底沙波形成与运移规律的理论模式。以此为基础建立了南海北部海域海底沙波波长及沙波移动的数学模型,对较大范围内的沙波形态及其运移规律进行了计算,成果表明计算区域海底沙波在正常水流条件下迁移速率相对较小,可视为比较稳定的地貌类型,为该海域海底工程实施提供参考。     

南方极端冰雪气候条件下冻土特征

2008年南方部分地区极端冻雪气候条件下形成的冻土,已成为工程界广泛关注的问题。通过对江西、湖南、湖北及广西省表土的调查与试验研究,对南方极端冰雪气候条件下冻土的特征进行了初步研究,认为南方冻土类型主要为短时冻土和瞬时冻土,对冻土的分布地区、冻胀等级、危害性进行了分析,为南方极端冰雪气候条件下冻土引发地质灾害的防治提供科学依据。     

Process control of the sand wave migration in Beibu Gulf of the South China Sea

Based on the environment characteristics of the Beibu Gulf of South China Sea, a quasi-three-dimensional physical model is built.By coupling the bottom boundary layer with the two-dimensional tidal current field near the seabed surface, the quasi-three-dimensional hydrodynamic numerical simulation is carried out.The sand wave migration process is dealt with by coupling the hydrodynamic model with the sediment transport model.The computational results are shown to be in good agreement with the observed data,...     

波生沿岸流数值模拟研究及其实验验证

本文在高阶近似抛物化缓坡方程求解大面积波浪场基础上，利用辐射应力的概念建立了波生沿岸流模型。通过与不同斜坡地形条件下具有不同 波高、周期的规则波及不规则波生流的物理模型实验结果比较，验证了数学模型应用的广泛性和正确性。本文着重分析了数学模型中水平涡粘系数的确定，并得出了沿岸流的一些规律性结论。     

南海东北部陆架波折处潮-地作用激发非线性内波的数值模拟

南海东北部陆架波折处是大振幅内孤立波的频发地带.普遍的观点认为,这些内孤立波主要源自于吕宋海峡处潮流与海脊的相互作用;而对局地潮流-陆架波折相互作用的生成过程了解较少.本文通过一个二维非静力近似海洋数值模式,模拟了南海东北部陆架波折处潮流-地形相互作用激发内波及内波的演化过程,探讨了潮流周期、跃层深度对内波生成过程的影响.研究表明,潮流与地形相互作用能够激发向岸传播的内孤立子波列,证实了该海区内孤立波局地生成的可能性,但是相比于从吕宋海峡处传入的大振幅内孤立波,局地生成的内孤立波振幅要小得多.     

Observation and simulation of wind waves near a typical reef lagoon in South China Sea

Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed near islands or inside a lagoon.This paper aims to find a feasible analysis tool for the wave simulations near islands and reefs.The proposed three methods of grid techniques of WAVEWATCH III(WW3)are assessed by using on-site measured data which was collected and accumulated for about 5 years since August 2014 by a wave observation system deployed inside and outside a reef lagoon in South China Sea.In the assessments,the wave statistics including the correlation coefficients,root mean square errors,and their variances are used to quantify the precisions of the simulation results of the significant wave heights,mean wave periods,and peak wave directions at two sites.Among the three methods,the Multi-scale Zone and Multi-scale grid Technique(MZMGT)established on unstructured triangular grids exhibits better results in terms of the accuracy and CPU cost.In addition,the bimodal feature of wave spectra was observed at both sites of the reef lagoon in different typhoon events.The wave characteristics inside the reef lagoon and open sea are also analyzed.     

The characteristics of waves around an entrance of a lagoon in South China Sea

The characteristics of the waves around a lagoon entrance in South China Sea were observed during the past one and half years based on the wave measurements.The...     

南海东北部海域潮汐模式的模型参数最优估计

利用深海高度计资料对南海东北部海域潮汐模式的模型参数进行了最优同化估计。模型参数包括底摩擦系数和开边界条件。得到的最优底摩擦系数的平均值为0.0085,取值较大的区域有台湾岛的东北部和西南部及吕宋海峡,而这些海域也是内潮响应较强烈的海域。     

基于 T/P 资料分析南海海面风、浪场特征及其关系

本文以T/P卫星高度计提供的海面风、浪资料为基础,利用自然正交函数对南海海面风、浪场进行展开,然后找出统计上显著的几个典型场,探讨南海海风、浪场的时空分布特征及其关系。分析结果显示,南海海面风、浪场的第一、第二模态具有很好的相似性,第三模态却表现出明显不同的特征,这一结果可以很好地反映南海海面风、浪场间的关系,从而为海浪场的经验预报和分析提供参考。     

南海海啸反问题预报模式

通过COMCOT海啸模型计算南海马尼拉海沟潜在震源区单元板块单位滑动产生的海啸波在区域内传播过程,将计算结果组成相应南海海啸波数据库.采用浮标监测数据与数据库结合通过最小二乘法构建南海海啸预报模式.以假想马尼拉海沟发生8.3级地震海啸为案例,应用预报模式对华南地区进行海啸预测,采用30 min和60 min监测数据分别反演计算,在三个近岸验证点的波高和正问题结果比较误差分别在25％和17％之内,到达时间及相位基本一致,预报的计算时间在2 min以内.     

某小水电站暴雨诱发地质灾害机理分析

四川峨边县吊尔咀滑坡由极端暴雨诱发形成。降雨使某小水电站引水渠出水口水位高于进水口约2 m,引起渠水倒灌并导致引水口检修孔溢水,水流侵蚀并逐步掏空水渠下方基础,致使水渠下部坡体受到冲刷形成泥石流,并进而引起上部坡体失稳产生滑坡。滑坡实例表明：在小水电站的设计中,应充分考虑当地的地形地质条件和气候条件,以避免留下致灾隐患。       

南海中尺度海域低放废水数值模拟研究

低放废水的排放一直是国内外关注的问题,目前国内多数研究采用小尺度海域模拟短期低放废水排放后的迁移扩散状况。以南海中尺度海域为例,采用MIKE模拟软件,分析南海中尺度海域的潮汐特征,模拟计算低放废水长期排放后的浓度场分布规律。研究表明:放射性核素氚的浓度场分布情况主要受到潮流场、余流的影响,雷州半岛东部低放废水排放情形下,放射性核素环抱于雷州半岛,并在北部湾迁移扩散,主要流向为西北和西南向;雷州半岛西部排放的主要流向为西北和西南向。就东西部低放废水排放比较而言,西部排放更加有利于低放废水的稀释扩散,排放口附近海域氚的浓度活度较高,对海洋环境敏感目标影响较小。     

南海珊瑚岛礁水域浅层地震反射波勘探

在南海某珊瑚岛礁的工程勘察中,采用快速高效的浅层水域地震反射波勘探方法配合钻探进行联合勘察,将钻孔的“点”与物探的“线”结合起来,相互对比、佐证,进行综合解释,查明了岛礁珊瑚松散沉积物的厚度、基岩起伏形态及大范围内的连续地质剖面。勘探结果为岛礁岩土工程性状调查、水文地质调查以及工程建设提供了可靠的地质依据和设计参数,取得了理想的效果。水域地震反射波对岛礁的不同地貌单元内礁坪、向海坡、潟湖、外海的沉积层界面反映清晰,但在外礁坪区域由于现代海滩岩的发育,声波较难穿透。     

南海浮式码头与系泊系统动力耦合分析

南海部分海域由于海底地形限制,运输船舶无法正常靠泊作业,可采用成本较低的浮式码头供运输船舶停泊使用。该文应用基于开源平台Open FOAM开发的船舶与海洋工程CFD求解器―naoe-FOAM-SJTU,对一座分布式系泊系统的浮式码头在入射波浪作用下的运动响应进行了数值模拟。文中系泊系统的求解采用基于集中质量法的动力分析方法,给出了码头运动和系泊系统所受动力的时历曲线,并且将结果同静力分析进行对比,验证了采用动力分析方法的可靠性和必要性。     

黄东海悬浮泥沙浓度的垂向分布特征及其回归模型

以1959年至2006年期间,东中国海域现场调查的24个航次4 813组悬浮物(泥沙)浓度数据资料为基础,采用相关分析和回归分析等方法,研究了东中国海域悬浮物浓度的垂向分布特征,给出了适用于不同季节、不同区域的悬浮物浓度的垂向分布模型.结果表明:悬浮物垂向浓度呈现明显的冬、春季高,夏、秋季低的特征;悬浮物浓度的大小与相对水深相关性良好,而水深对悬浮物浓度的影响则表现在其垂向梯度变化方面:垂向浓度梯度在长江口至杭州湾一带的河口区(A类站)呈现出高值,在与海岸线平行的苏北浅滩至闽浙沿岸的近滨区(B类站)呈现中值,外滨(C类站)的广大海域则呈现明显的低值;春、夏、秋、冬四个季节近滨区B类站分布范围分别与10～30m,10～20m,10～20m,20～40m的等深线区域相吻合,其范围的季节变化与黄东海水动力条件的季节变化密切相关.利用悬浮物垂向浓度模型可以由已知的海水表层浓度计算得到不同水层的悬浮物浓度,其有效性检验和拟合结果检验表明,该模型置信度较高,且能够更为有效的预报海水中、上层水体的悬浮物浓度值.     

开阔海域越洋海啸波高计算的一种简化方法

该文研究了开阔海域中越洋海啸波高的简化计算方法。基于选取具有一系列断裂带长宽比的震源参数,采用Okada弹性变形理论生成初始海底变形,运用基于有限体积法的非线性浅水方程数值模型,模拟地震激发海啸在4 000 m水深的平底地形上的传播过程。通过监测布置在相对震源中心不同距离及方位角上测点的波面时间序列,研究海啸波高在不同距离及方位角上的分布规律,给出不同断裂带长宽比下越洋海啸传播过程中首波幅值的分布关系式;进一步分析了断裂带长宽比对模型参数的影响,得出了归一化的越洋海啸波高计算经验公式,并与日本2011年海啸实际记录进行对比,验证了该近似方法的有效性。     

Spatial and temporal variations in algal blooms in the coastal waters of the western South China Sea

Algal blooms occur frequently in the coastal waters of the western South China Sea (SCS). This paper reports spatial and temporal variations of algal bloom events in these waters from 1993 to 2007. Twenty-five algal bloom events occurred in summer in the coastal waters of South and Central Vietnam where they were associated with wind-induced, coastal, nutrient upwelling and river discharges; a further eight events occurred in the coastal waters of North Vietnam. A greater number of algal bloom events were observed in 1999 and 2002, and were accompanied by several previously unobserved species for the study period. These events may be related to the El Niño events of 1998 and 2002. Furthermore, the bloom-causative species Trichodesmium erythraeum (Cyanophyta) entirely dominated the phytoplankton community of algal blooms during 1993–1999 whereas the species Phaeocystis globosa (Haptophyta) dominated blooms after 2002. This study establishes a basis for further long-term research of algal bloom event variations, and provides a compiled scientific reference that may be used for later prediction of Harmful algal blooms (HABs).     

Mathematical model of wave transformation over radial sand ridge field on continental shelf of South Yellow Sea

According to a deformed mild-slope equation derived by Guang-wen Hong and an enhanced numerical method,a wave refraction-diffraction nonlinear mathematical model that takes tidal level change and the high-order bathymetry factor into account has been developed.The deformed mild-slope equation is used to eliminate the restriction of wave length on calculation steps.Using the hard disk to record data during the calculation process,the enhanced numerical method can save computer memory space to a certain extent,so that a large-scale sea area can be calculated with high-resolution grids.This model was applied to wave field integral calculation over a radial sand ridge field in the South Yellow Sea.The results demonstrate some features of the wave field:(1)the wave-height contour lines are arc-shaped near the shore;(2)waves break many times when they propagate toward the shore;(3)wave field characteristics on the northern and southern sides of Huangshayang are different;and(4)the characteristics of wave distribution match the terrain features.The application of this model in the region of the radial sand ridge field suggests that it is a feasible way to analyze wave refraction-diffraction effects under natural sea conditions.